The History of the Earth
Did the Earth always look like this?
Geology
• Geology is the study
of rocks and the Earth
• “Geologists” study the
Earth’s crust and the
rocks, mountains, and
volcanoes
History of the Earth
• “Geologic Time” is the
scientific theory of the
history of the Earth
• Scientists divide the
Earth’s history into 4
“Eras”
–
–
–
–
The Precambrian
The Paleozoic
The Mesozoic
The Cenozoic
PRECAMBRIANThe Beginning
• The Earth formed 4.6
BILLION years ago
• At first, the Earth was
a huge ball of molten
rock
PRECAMBRIAN
• There was no solid
rock, no oxygen, no
living things, no water
• After about 700
million years, the
planet cooled and the
first solid rocks
formed
PRECAMBRIAN
• As the Earth cooled,
water vapour (gas) from
volcanoes condensed
• Rain fell and made
oceans
PRECAMBRIAN
• After over 1 billion
years, bacteria
formed.
• After 2 billion years,
jellyfish!
PALEOZOIC
• All the continents
crash into each other
• They form a giant
continent called
Pangaea
PALEOZOIC
•
•
•
•
•
Fish with shells
Plants
Insects
Reptiles
Trees
MESOZOIC
• Pangaea breaks apart
• The “age of the
dinosaurs”
• Dinosaurs all die (go
extinct)
• This is an “extinction”
because of a meteor
CENOZOIC
• The continents move
to their current places
• In the future?
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CENOZOIC
• The Age of Mammals
(horses, cats, dogs,
rodents, primates)
• The first early
humans (about 10
000 years ago)
• We live in the
Cenozoic Era
Key Ideas:
•
•
•
•
•
The Earth is very old
Humans have only appeared on Earth
“recently”
The Earth has not always looked like this!
There have been different climates,
environments, species and continents!
The Earth is always changing!